Design and Performance Analysis of High-Speed Cryogenic Permanent Magnet Synchronous Motor

The cryogenic motor is the core component of the liquefied natural gas (LNG) submersible pump, which is completely submerged in LNG during operation. Since its working environment is quitely different from that of ordinary temperature motor, the design of cryogenic motor has its own special characteristics. According to the particularity and requirements of cryogenic motors, two permanent magnet synchronous motors (PMSM) with the same basic structure are proposed in this paper, one is an integer slot winding motor and the other is a fractional slot winding motor. Although the two motors have different pole pairs, they share the same pole arc coefficient. In order to achieve the same no-load back electromotive force (EMF), the two motors adopt different magnetic pole thickness. The harmonic analysis of the winding magnetic potential of the two motors is carried out by Matlab software, and the performance of both motors is calculated by finite element software. It is found that the fractional slot winding motor has the advantage of weakening cogging torque, smoothing torque output, reducing core loss and improving motor efficiency.